What is the difference between MySQL development environment and test environment??

I can tell the difference between them and the production environment , But I don't know the difference between them .
Only the production environment is really put into use , User oriented , Neither the test environment nor the development environment is user oriented . In that case , Why should it be divided into testing and development ？
The data in the development environment should also be simulated ？ It can't be real user data ？